Anesthesia machines are well known in the art and used to anesthetize humans as well as other animals most often for surgical purposes. Virtually all prior art anesthetic machines are intended to be fixedly mounted in a stable environment. This is usually required by the design of the machine and especially the vaporizer wherein the liquid anesthetic agent is contained. Should the anesthetic machine be jostled, or its attitude be changed such as by tilting or the like, control of the rate of evaporation of the liquid anesthetic is affected and, in extreme cases of tilting or inversion, liquid agent may be directly introduced into the various passageways such that the patient could be directly exposed to dangerous levels of agent. Such a circumstance would result in disastrous consequences.
Examples of prior art anesthetic machines and vaporizers may be found in U.S. Pat. Nos. 5,144,991; 4,879,997; 4,693,853; 3,687,137; 3,851,645; and U.S. Pat. No. 3,838,687. Of these, U.S. Pat. No. 3,838,687 discloses a wheeled table with an anesthetic apparatus slidably suspended below the tabletop such that it might be transported with the table as the patient on the table is moved. However, its fixed orientation prevents it from being tilted to any great extent and its construction is not directed to withstanding severe changes in its physical attitude. Other prior art devices presently commercially available suggest that they are attitude insensitive. However, in one device its construction utilizes open passageways which would readily permit the flow of liquid anesthetic agent therethrough and to the patient and hence is dangerously unacceptable. In another commercial device, a baffled wick assembly is utilized by being submersed in a generally cylindrical vaporizer chamber such that it would take 24-48 hours to clear the wick for any other liquid anesthetic agent to be used and, furthermore, it is believed that excessive tilting, jostling, or inversion of the vaporizer would tend to saturate significantly greater sections of the baffled wick such that performance would move out of clinically safe tolerance levels and present undue risk to the patient.
In order to solve these and other problems of the prior art, the inventors herein have succeeded in designing and developing an attitude insensitive anesthesia machine which is transportable, useable with any one of four industry standard liquid anesthetic agents, has a calibrated flow control manifold for the use of multiple carrier gases including a flush bypass for delivery of oxygen bursts, and which includes at its heart an improved vaporizer design having a combinant chamber with a pair of diluent stems having orifices which remain above the level of liquid anesthetic agent despite the physical orientation thereof. A baffle which is arcuately shaped and generally concentric with each diluent stem is mounted thereto and covers the orifice to divert the vapor flow into a circuitous path. Additionally, a thin cotton wick is mounted to and extends vertically along the height of each of two carrier stems. All of these features, and others, combine to provide a portable anesthesia machine which may be readily transported, used in virtually any physical attitude, is elegantly simple in design and correspondingly inexpensive, and which is ruggedized for field use under hostile environmental conditions.
More particularly, an important element of the present invention includes the vaporizer design itself which incorporates a combinant chamber wherein the liquid anesthetic agent resides upon the vaporizer being charged. A pair of generally cylindrical diluent stems extend in generally parallel fashion into the interior of the combinant chamber with each stem having an orifice located near its end and with the orifices generally facing each other and near the center of the combinant chamber such that the liquid anesthetic agent does not pour into the orifices no matter what orientation or physical attitude the vaporizer is placed in. Additionally, a generally cylindrical baffle is mounted to each diluent stem proximate the orifice with a slotted opening in the baffle on the opposite side of the diluent stem to thereby force vapor traveling between the orifices to traverse a circuitous path. With this arrangement, even though the orifices directly face each other, the carrier gas must traverse a substantial portion of the interior of the combinant chamber which leads to an effective mixing with vapor from the anesthetic agent. Thus, this arrangement permits the orifices to be physically oriented in their central location so as to accommodate jostling, tilting, and movement of the device without affecting operation. A thin cotton wick is mounted to each of the carrier stems to further aid in mixing of the carrier gas and anesthetic. As the wicks become saturated through contact with the liquid agent, it normalizes the rate of evaporation for the liquid agent to also normalize the delivery of anesthesia to the patient. The flow of carrier gas into the combinant chamber is controlled through a novel calibrated knob assembly which includes a pair of pistons and cylinders associated with the diluent stems, an actuator plate, and a roller bearing and helical ramp which moves the pistons within the cylinders in tandem to open and close the inlets to the diluent stems and also divert carrier gas between the anterior chamber and the combinant chamber. The pistons may also be advanced within the cylinders to entirely close off the diluent stems to permit the vaporizer to be transported while charged.
Liquid anesthetic agent is charged into and discharged from the combinant chamber through a well fill port. This meets various federal safety guidelines and also provides an ease of use and operability for the vaporizer unavailable in the prior art.
A multi-port flow control manifold provides still a further novel feature of the present invention as multiple carrier gases may be readily connected to the manifold and flow of any one or more of the carrier gases may be controlled and adjusted under calibration through the flow control manifold. The flow control manifold also provides a bypass flush line for delivering a flushing burst of oxygen to the patient.
While the principal advantages and features of the present invention have been explained above, a greater understanding of the invention may be obtained through reference to the drawings and detailed description which follow.